1. Field of the Invention
The present invention pertains to method for applying a zipper to a web, particularly a relatively narrow zipper in a direction transverse to the film direction in a form fill and seal apparatus.
2. Description of the Prior Art
In the prior art, form fill and seal apparatus and methods are known. While these methods and apparatus have been extremely successful for the high speed packaging of various kinds of foodstuffs, improvement is desired with respect to the application of narrow zippers in the direction transverse to the direction of the film. More particularly, improvement is desired with respect to the handling of narrow zippers during installation.
The present invention provides an applicator which uses a series of grooved rollers or a grooved guide plate to trap the zipper as it is being fed across the web. When in position, the web momentarily stops to allow the seal bar to tack the zipper to the film from below the film. The rollers and guide plate act as an anvil to provide pressure from the seal bar. The rollers, guide plate and seal bars then retract to allow the film to index forward. After the cylindrical shape of the bag or other container has been formed, the bottom and top bag seal jaws close. The zipper seal bars then apply heat and pressure to the zipper to tack and seal the zipper to both sides of the bag.
More particularly, a guide system is used to guide and move the zipper in a precise position perpendicular or transverse to the direction of the web. This system of rollers provide positive tensioning to the zipper by increasing the speed over the zipper feed roller. It also allows a wide range of lengths to be fed because there will always be at least one roller in contact with the zipper. The roller assembly will further retract from the zipper guide plate to allow the zipper, which is attached to the film at the station, to travel with the film without interference.
Additionally, seal bar assemblies are used with a first seal bar for forming the upper transverse seal on a package along with a second seal bar for forming the lower transverse seal on a subsequent package.